Generally, an electric vehicle is provided with many components generating heat, such as a battery, a drive motor, and other electric devices. However, if these components are overly heated, efficiency thereof may be lowered. Accordingly, an additional cooling apparatus is required to cool the components.
Of these components, in the case of the drive motor that rotates wheels of the electric vehicle, a water-cooled cooling apparatus using an electric water pump (EWP), and an air-cooled cooling apparatus using a pulse-width modulation (PWM) cooling fan are used as the cooling apparatus. The above cooling methods may help to improve fuel efficiency by controlling an output of the cooling apparatus to cool the drive motor by a required cooling rate.
As shown in FIGS. 1, 2A, and 2B, conventionally, the output of the cooling apparatus is controlled to be in proportion to a vehicle speed. In other words, when a vehicle currently running at a speed of D enters an S-curved road, the vehicle is decelerated at speeds of C, B, and A according to its location on the road. After that, as the vehicle moves from the S-curved road, the vehicle is accelerated at speeds of B, C, and D.
Here, a graph of a vehicle speed shown in FIG. 2A and a graph of an output of a cooling apparatus shown in FIG. 2B have the same shape, and it is recognized that the vehicle speed and the output of the cooling apparatus are controlled to be in proportion to each other.
However, in the case of sudden deceleration of the vehicle, the output of the cooling apparatus is also dramatically decreased, and thereby residual heat remaining in the drive motor cannot be removed, and accordingly, efficiency of the drive motor is lowered. Further, in the case of sudden acceleration of the vehicle from a low speed, temperature of the drive motor rises since the output is insufficient to efficiently cool heat generated from the drive motor even when the output of the cooling apparatus is increased.
Accordingly, a new method of cooling control is required to efficiently cool the drive motor when the vehicle speed is suddenly changed.
The foregoing is intended merely to aid in the understanding of the background of the present invention, and is not intended to mean that the present invention falls within the purview of the related art that is already known to those skilled in the art.